[RFA 4/6] Remove some variables but call functions for side effects

[Tom Tromey <tom@tromey.com>]

This patch consolidates the (possibly-questionable) spots where we
remove a declaration but continue to call some function for side
effects.  In a couple of cases it wasn't entirely clear to me that
this mattered; and in some other cases it might be more aesthetically
pleasing to use ATTRIBUTE_UNUSED.  So, I broke this out into a
separate patch for simpler review.

2016-06-06  Tom Tromey  <tom@tromey.com>

	* arch-utils.c (default_skip_permanent_breakpoint): Remove
	"bp_insn".
	* disasm.c (do_assembly_only): Remove "num_displayed".
	* dwarf2read.c (read_abbrev_offset): Remove "length".
	(dwarf_decode_macro_bytes) <DW_MACINFO_vendor_ext>: Remove
	"constant".
	* m32c-tdep.c (make_regs): Remove "r2hl", "r3hl", and "intbhl".
	* microblaze-tdep.c (microblaze_frame_cache): Remove "func".
	* tracefile.c (trace_save): Remove "status".
---
 gdb/ChangeLog         | 12 ++++++++++++
 gdb/arch-utils.c      |  3 +--
 gdb/disasm.c          |  4 +---
 gdb/dwarf2read.c      |  9 +++++----
 gdb/m32c-tdep.c       |  9 +++------
 gdb/microblaze-tdep.c |  4 ++--
 gdb/tracefile.c       |  7 ++++---
 7 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9839c55..b164911 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,17 @@
 2016-06-06  Tom Tromey  <tom@tromey.com>
 
+	* arch-utils.c (default_skip_permanent_breakpoint): Remove
+	"bp_insn".
+	* disasm.c (do_assembly_only): Remove "num_displayed".
+	* dwarf2read.c (read_abbrev_offset): Remove "length".
+	(dwarf_decode_macro_bytes) <DW_MACINFO_vendor_ext>: Remove
+	"constant".
+	* m32c-tdep.c (make_regs): Remove "r2hl", "r3hl", and "intbhl".
+	* microblaze-tdep.c (microblaze_frame_cache): Remove "func".
+	* tracefile.c (trace_save): Remove "status".
+
+2016-06-06  Tom Tromey  <tom@tromey.com>
+
 	* symfile.c (simple_overlay_update_1): Comment out initialization
 	of "size".
 	(simple_overlay_update): Likewise.
diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c
index 604042f..53121bc 100644
--- a/gdb/arch-utils.c
+++ b/gdb/arch-utils.c
@@ -857,10 +857,9 @@ default_skip_permanent_breakpoint (struct regcache *regcache)
 {
   struct gdbarch *gdbarch = get_regcache_arch (regcache);
   CORE_ADDR current_pc = regcache_read_pc (regcache);
-  const gdb_byte *bp_insn;
   int bp_len;
 
-  bp_insn = gdbarch_breakpoint_from_pc (gdbarch, &current_pc, &bp_len);
+  gdbarch_breakpoint_from_pc (gdbarch, &current_pc, &bp_len);
   current_pc += bp_len;
   regcache_write_pc (regcache, current_pc);
 }
diff --git a/gdb/disasm.c b/gdb/disasm.c
index f611721..bd1f760 100644
--- a/gdb/disasm.c
+++ b/gdb/disasm.c
@@ -737,13 +737,11 @@ do_assembly_only (struct gdbarch *gdbarch, struct ui_out *uiout,
 		  CORE_ADDR low, CORE_ADDR high,
 		  int how_many, int flags, struct ui_file *stb)
 {
-  int num_displayed = 0;
   struct cleanup *ui_out_chain;
 
   ui_out_chain = make_cleanup_ui_out_list_begin_end (uiout, "asm_insns");
 
-  num_displayed = dump_insns (gdbarch, uiout, di, low, high, how_many,
-                              flags, stb, NULL);
+  dump_insns (gdbarch, uiout, di, low, high, how_many, flags, stb, NULL);
 
   do_cleanups (ui_out_chain);
 }
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 6658a38..58b502b 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -4497,12 +4497,12 @@ read_abbrev_offset (struct dwarf2_section_info *section,
 {
   bfd *abfd = get_section_bfd_owner (section);
   const gdb_byte *info_ptr;
-  unsigned int length, initial_length_size, offset_size;
+  unsigned int initial_length_size, offset_size;
   sect_offset abbrev_offset;
 
   dwarf2_read_section (dwarf2_per_objfile->objfile, section);
   info_ptr = section->buffer + offset.sect_off;
-  length = read_initial_length (abfd, info_ptr, &initial_length_size);
+  read_initial_length (abfd, info_ptr, &initial_length_size);
   offset_size = initial_length_size == 4 ? 4 : 8;
   info_ptr += initial_length_size + 2 /*version*/;
   abbrev_offset.sect_off = read_offset_1 (abfd, info_ptr, offset_size);
@@ -21578,9 +21578,10 @@ dwarf_decode_macro_bytes (bfd *abfd,
 	  if (!section_is_gnu)
 	    {
 	      unsigned int bytes_read;
-	      int constant;
 
-	      constant = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	      /* This reads the constant, but since we don't recognize
+		 any vendor extensions, we ignore it.  */
+	      read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
 	      mac_ptr += bytes_read;
 	      read_direct_string (abfd, mac_ptr, &bytes_read);
 	      mac_ptr += bytes_read;
diff --git a/gdb/m32c-tdep.c b/gdb/m32c-tdep.c
index 59927a6..1e98f73 100644
--- a/gdb/m32c-tdep.c
+++ b/gdb/m32c-tdep.c
@@ -823,9 +823,6 @@ make_regs (struct gdbarch *arch)
   struct m32c_reg *sp;
   struct m32c_reg *r0hl;
   struct m32c_reg *r1hl;
-  struct m32c_reg *r2hl;
-  struct m32c_reg *r3hl;
-  struct m32c_reg *intbhl;
   struct m32c_reg *r2r0;
   struct m32c_reg *r3r1;
   struct m32c_reg *r3r1r2r0;
@@ -889,9 +886,9 @@ make_regs (struct gdbarch *arch)
 
   r0hl        = CHL (r0, tdep->int8);
   r1hl        = CHL (r1, tdep->int8);
-  r2hl        = CHL (r2, tdep->int8);
-  r3hl        = CHL (r3, tdep->int8);
-  intbhl      = CHL (intb, tdep->int16);
+  CHL (r2, tdep->int8);
+  CHL (r3, tdep->int8);
+  CHL (intb, tdep->int16);
 
   r2r0        = CCAT (r2,   r0,   tdep->int32);
   r3r1        = CCAT (r3,   r1,   tdep->int32);
diff --git a/gdb/microblaze-tdep.c b/gdb/microblaze-tdep.c
index 9cfe3fe..665ec0c 100644
--- a/gdb/microblaze-tdep.c
+++ b/gdb/microblaze-tdep.c
@@ -437,7 +437,6 @@ microblaze_frame_cache (struct frame_info *next_frame, void **this_cache)
 {
   struct microblaze_frame_cache *cache;
   struct gdbarch *gdbarch = get_frame_arch (next_frame);
-  CORE_ADDR func;
   int rn;
 
   if (*this_cache)
@@ -451,7 +450,8 @@ microblaze_frame_cache (struct frame_info *next_frame, void **this_cache)
   for (rn = 0; rn < gdbarch_num_regs (gdbarch); rn++)
     cache->register_offsets[rn] = -1;
 
-  func = get_frame_func (next_frame);
+  /* Call for side effects.  */
+  get_frame_func (next_frame);
 
   cache->pc = get_frame_address_in_block (next_frame);
 
diff --git a/gdb/tracefile.c b/gdb/tracefile.c
index c32bcf4..56fb0d2 100644
--- a/gdb/tracefile.c
+++ b/gdb/tracefile.c
@@ -57,7 +57,6 @@ trace_save (const char *filename, struct trace_file_writer *writer,
 	    int target_does_save)
 {
   struct trace_status *ts = current_trace_status ();
-  int status;
   struct uploaded_tp *uploaded_tps = NULL, *utp;
   struct uploaded_tsv *uploaded_tsvs = NULL, *utsv;
 
@@ -77,8 +76,10 @@ trace_save (const char *filename, struct trace_file_writer *writer,
     }
 
   /* Get the trace status first before opening the file, so if the
-     target is losing, we can get out without touching files.  */
-  status = target_get_trace_status (ts);
+     target is losing, we can get out without touching files.  Since
+     we're just calling this for side effects, we ignore the
+     result.  */
+  target_get_trace_status (ts);
 
   writer->ops->start (writer, filename);
 
-- 
2.5.5